Regeneration of the periodontal tissues lost due to periodontal disease is one of ultimate goals of periodontal therapy. Current evidence indicates that the progenitor cells for the formation of new connective tissue attachment (new cementum with inserting fibers) on denuded roots are located in the underlying healthy part of the periodontal ligament. The attachment of cells to substrata, their migration, deposition and organization of extracellular matrix are not completely understood. The proposed studies are aimed at elaborating the biologic bases for tissue regeneration in periodontal therapy. Using an in vitro model for the periodontal ligament (PDL) developed in our laboratory, we will analyze the attachment of cells to dental substrata (root dentin, bone) and the organization of extracellular matrix by the cells. Specifically, we will be analyzing the roles of extracellular matrix components (fibronectin, collagen and osteonectin) on cell attachment, migration and differentiation. Reconstituted matrices in simulated periodontal spaces in vitro will be used. By combining in vitro and in vivo techniques, we will determine the ability of gingival, periodontal ligament and alveolar bone-derived cells to form new cementum with inserting fibers on dentin surfaces. Human gingival, PDL and alveolar bone-derived cells will be cultured, characterized, labelled, attached to dentin particles and implanted in nude mice. Finally, regeneration of the periodontal ligament requires the directed migration of progenitor cells. Using chemotactic assays, we will compare the migration rates of cells obtained from gingival, PDL and bone granulation tissue. Also, the attachment of these cells to collagen coated substrata and their cytoskeletal organization during directed migration will be analyzed. Information obtained from the proposed experiments will help us develop a new therapeutic procedure for the predictable regeneration of periodontal ligament. such information is also essential for a better understanding of the physiology of periodontal tissues.